The structures of Coulomb crystals formed from growing particles in a plasma have been finely observed with a charge coupled device video camera and the formation process has been analyzed by the Mie-scattering ellipsometry. It has been shown that the structure of Coulomb crystals growing orientedly to the direction perpendicular to electrodes are classified into 3 groups. Smaller particles tend to form the structures of three-dimensional piling of two-dimensionally close-packing horizontal layers. The structure of close-packing of strings is formed by larger particles. It is suggested that interaction between electric dipoles due to the polarization of negatively charged particles and the surrounding ions plays an important role in the determination of the structures.
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